1. Field of the Invention
The invention relates to a torsional vibration damper for a motor vehicle transmission having a drive-side transmission element which is rotatable about an axis of rotation, an output-side transmission element which is rotatable relative to the drive-side transmission element and a damping device connected between the drive-side and output-side transmission elements, wherein tile damping device comprises two gear elements which are connectable via toothings on each of the gear elements.
2. Description of the Related Art
A torsional vibration damper is known from German Utility Patent DE 94 14 314 that has a drive-side transmission element and an output-side transmission element rotatable relative thereto. The two transmission elements have at least one centrifugal mass each and are connected to each other via a damping device. The damping device has gear elements of a planetary gear set, for example, an annulus or planetary wheels, engaged therewith. Each of these gear elements is embodied with a set of teeth extending in the radial direction, with which a meshing connection with the other respective gear element is established.
When a torsional vibration damper is equipped with gear elements of this type, the gear elements accelerate during the transmission of torsional vibrations, and execute a movement relative to the transmission element that holds them. As a result, the mass inertia moment, which counteracts equidirectional fluctuations of the drive, is higher than it should be based on the mass of the torsional vibration damper. Thus, torque fluctuations at the engine front can be damped especially effectively by the increased mass inertia moment up to an engine speed of approximately 2500 RPM. However, the placement of the set of teeth at the radially outer region, with the gaps between each two teeth in the circumferential area located at the greatest distance from the rotational axis, reduces the amount of producible mass inertia moment for each planetary gear. This may be compensated for by positioning mass rings or mass disks axially adjacent to the toothing, for example. However, this measure enlarges the axial extension of the torsional vibration damper, something that is absolutely to be avoided, especially in smaller vehicles.
Above 2500 RPM, the torsional vibrations produced by the drive, e.g., an internal combustion engine, become ever more higher in frequency, but also ever smaller in amplitude. In this situation, the higher mass inertia moment produced by the gear elements acts disadvantageously compared to a torsion vibration damper without such gear elements. The prior art reference discloses no measures to solve this problem.
At speeds below 2500 RPM, torsional vibration dampers without gear elements between the drive-side and output-side transmission elements, as known, for example, from German reference DE 36 30 398 A1, display poorer behavior than the torsional vibration dampers with the gear elements as described above due to their relatively smaller mass inertia moment. On the other hand, at speeds above 2500 RPM, such torsional vibration dampers are better suited to filter out the high-frequency vibrations that have small amplitudes.